hgext/fsmonitor/watchmanclient.py

revlog-split: show manifest data loss situation when using clonebundle

After the commit of the transaction from applying the clone bundle, changes to
the manifest from the subsequent pull would write index data in the wrong file.
This lead to data being "lost" after the pull and the repository to be
corrupted. We add a test checking this specific scenario.

In practice, the issue only affects the manifest but we also test the issue with a file for future proofing things up.

See test documentation and failure for details.

# watchmanclient.py - Watchman client for the fsmonitor extension
#
# Copyright 2013-2016 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


import getpass

from mercurial import (
    encoding,
    util,
)
from mercurial.utils import (
    procutil,
    stringutil,
)

from . import pywatchman


class Unavailable(Exception):
    def __init__(self, msg, warn=True, invalidate=False):
        self.msg = msg
        self.warn = warn
        if self.msg == b'timed out waiting for response':
            self.warn = False
        self.invalidate = invalidate

    def __bytes__(self):
        if self.warn:
            return b'warning: Watchman unavailable: %s' % self.msg
        else:
            return b'Watchman unavailable: %s' % self.msg

    __str__ = encoding.strmethod(__bytes__)


class WatchmanNoRoot(Unavailable):
    def __init__(self, root, msg):
        self.root = root
        super(WatchmanNoRoot, self).__init__(msg)


class client:
    def __init__(self, ui, root, timeout=1.0):
        err = None
        if not self._user:
            err = b"couldn't get user"
            warn = True
        if self._user in ui.configlist(b'fsmonitor', b'blacklistusers'):
            err = b'user %s in blacklist' % self._user
            warn = False

        if err:
            raise Unavailable(err, warn)

        self._timeout = timeout
        self._watchmanclient = None
        self._root = root
        self._ui = ui
        self._firsttime = True

    def settimeout(self, timeout):
        self._timeout = timeout
        if self._watchmanclient is not None:
            self._watchmanclient.setTimeout(timeout)

    def getcurrentclock(self):
        result = self.command(b'clock')
        if not util.safehasattr(result, 'clock'):
            raise Unavailable(
                b'clock result is missing clock value', invalidate=True
            )
        return result.clock

    def clearconnection(self):
        self._watchmanclient = None

    def available(self):
        return self._watchmanclient is not None or self._firsttime

    @util.propertycache
    def _user(self):
        try:
            return getpass.getuser()
        except KeyError:
            # couldn't figure out our user
            return None

    def _command(self, *args):
        watchmanargs = (args[0], self._root) + args[1:]
        try:
            if self._watchmanclient is None:
                self._firsttime = False
                watchman_exe = self._ui.configpath(
                    b'fsmonitor', b'watchman_exe'
                )
                self._watchmanclient = pywatchman.client(
                    timeout=self._timeout,
                    useImmutableBser=True,
                    binpath=procutil.tonativestr(watchman_exe),
                )
            return self._watchmanclient.query(*watchmanargs)
        except pywatchman.CommandError as ex:
            if 'unable to resolve root' in ex.msg:
                raise WatchmanNoRoot(
                    self._root, stringutil.forcebytestr(ex.msg)
                )
            raise Unavailable(stringutil.forcebytestr(ex.msg))
        except pywatchman.WatchmanError as ex:
            raise Unavailable(stringutil.forcebytestr(ex))

    def command(self, *args):
        try:
            try:
                return self._command(*args)
            except WatchmanNoRoot:
                # this 'watch' command can also raise a WatchmanNoRoot if
                # watchman refuses to accept this root
                self._command(b'watch')
                return self._command(*args)
        except Unavailable:
            # this is in an outer scope to catch Unavailable form any of the
            # above _command calls
            self._watchmanclient = None
            raise